Control means for a cooking apparatus or the like

ABSTRACT

This disclosure relates to an electrical control system for an oven having a bake heater and a broil heater to be operated by a power source having a neutral line and a pair of powerlines, the control means operating the bake heater at substantially full rated power and the broil heater at part of its rated power when the oven is set for maintaining a selected bake temperature below a broil temperature and above approximately 300* F. and the system demands heat input, whereas the control means operates both of the bake and broil heaters at part-rated power thereof in interconnecting the bake and broil heaters in series across one powerline and the neutral line when the temperature of the oven is above the selected bake temperature.

United States Patent Siegfried E. Manecke CONTROL MEANS FOR A COOKING APPARATUS OR THE LIKE 12 Claims, 4 Drawing'Figs.

US. Cl 219/515 Int. Cl 1105b l/02 Field of Search t. 219/494, 515,449,4l2,413,414

References Cited UNITED STATES PATENTS 3,358,122 12/1967 Torrey 219/413 6/1960 Wantz et al 219/515 3,358,121 12/1967 Bowling ABSTRACT: This disclosure relates to an electrical control system for an oven having a bake heater and a broil heater to be operated by a power source having a neutral line and a pair of powerlines, the control means operating the bake heater at substantially full rated power and the broil heater at part of its rated power when the oven is set for maintaining a selected bake temperature below a broil temperature and above approximately 300 F. and the system demands heat input, whereas the control means operates both of the bake and broil heaters at part-rated power thereof in interconnecting the bake and broil heaters in series across one powerline and the neutral line when the temperature of the oven is above the selected bake temperature.

PATENTEU nm 1 2 mm SHEET 10F 2 FIG! INVENTOR SIEGFRIED E. MANECKE HIS ATTORNEYS PATENTED acumen 3,612,327

SHEET 2 OF 2 SET FOR BAKE ABOVE 3OOOF BROIL -l9 SET FOR BROIL INVENTOR S'EGFRIED E. MANECKE FIG.4 20

HIS ATTORNEYS CONTROL MEANS FOR A COOKING APPARATUS OR THE LIKE This invention relates to an improved control system and method for operating an electrical oven having a bake heater and a broil heater, this invention also relating to an improved control device for such an oven control system or method.

It is well known that various control systems have been provided for electrical ovens wherein the bake heater is adapted to be placed across the two powerlines of a three-wire power source and the broil heater is simultaneously adapted to be placed across one of the powerlines and the neutral line when the oven has been set for a baking temperature. Thus, when the temperature-sensing means of such a control system senses a condition for heat input, the bake heater operates at fullrated power while the broil heater operates at approximately one-quarter of its rated power. However, when such a priorknown control system no longer demands heat input for such a bake setting thereof, the operation of both the bake and broil heaters is terminated until the temperature-responsive device again senses a condition for heat input.

It has been found that such a control system has a tendency to provide a relatively wide temperature range of overshoot and undershoot when a bake temperature has been selected below a broil temperature and above a predetermined bake temperature, such as 300 F.

Accordingly, one feature of this invention is to provide an oven control system of the above type wherein the complete termination of the bake and broil heaters during a higher selected bake temperature operation of the oven is not permitted even though the temperature of the oven has reached the selected high bake temperature.

In particular, the control means of this invention is so constructed and arranged in a manner hereinafter set forth to operate the bake heater at substantially full-rated power and the broil heater at part-rated power when the control means is set for maintaining a selected bake temperature below a broil temperature and above a predetermined bake temperature during the time that the temperature of the oven is below the selected bake temperature, the control means subsequently operating both the bake heater and broil heater at part-rated power thereof when the temperature of the oven is above the selected bake temperature whereby an adverse wide temperature overshoot and undershoot range is not provided by the control means of this invention.

Therefore, it is an object of this invention to provide an improved oven control system having one or more of the novel features set forth above or hereinafter shown or described.

Another object of this invention is to provide an improved method for operating an electrical oven system or the like, the method of this invention having one or more of thenovel features set forth above or hereinafter described.

Another object of this invention is to provide an improved control device for such an oven control system or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is a schematic view illustrating the control system, method and control device of this invention when set in its off position.

FIG. 2 is a view similar to FIG. 1 with the control system set for maintaining a bake temperature below a predetermined bake temperature.

FIG. 3 is a view similar to FIG. 1 and illustrates the control system for maintaining a bake temperature above the predetermined bake temperature and below a broil temperature.

FIG. 3A is a partial view similar to FIG. 3 and illustrates the system as set for the condition of FIG. 3 when the temperature-responsive means has opened one of the powerlines of the power source.

FIG. 4'is a view similar to FIG. I and illustrates the control system set for a broiling operation.

While the various features of this invention are hereinafter set forth and illustrated as being particularly adaptable for operating a bake heater and a broil heater of the same rated power, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide an operation of other types of electrical heaters or the like.

Therefore, this invention is not to be limited to only the embodiments illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIG. I, the improved electrical oven control systemand method of this invention is generally indicated by the reference numeral 10 and is illustrated as controlling the heating operation of a domestic oven or the like generally indicated by the reference numeral 11 and only schematically illustrated in FIG. I.

The control 'system 10 includes a three-wire electrical power source that comprises two powerlines L' and L and a neutral line N in a conventional manner. In addition, the control system 10 includes a conventional bake heater or electrical element 12 for the oven 11 and a conventional broil heater or electrical element 13 for the oven 11.

The control device of this invention for operating the system 10 is generally indicated by the reference numeral 14 and comprises a housing means 15 that carries a temperatureresponsive device 16 and three electrical switch means I7, 18 and 19 that are respectively controlled by a manual manipulator means 20 of the control device 14 in a manner hereinafter described.

The electrical switch 17 includes a pair of electrical contacts 21 and 22 adapted to be bridged by a bridging member 23 of a switch arm 24 fulcrumed to the housing 15 at the end 25 thereof in amanner hereinafter described. The contact 21 of the switch 17 is interconnected to the power source lead L by a lead 26 and the contact 22 of the switch 17 is interconnected to a lead 27 that is respectively interconnected to the sides 28 and 29 of the bake heater I2 and broil heater 13.

The temperature-responsive device I6 comprises a contractable and expandable power element 16 or the like that is adjustable relative to the housing 15 and has an interior chamber interconnected to a temperature-sensing bulb 30 disposed in the oven 11 by a conventional capillary tube 31 whereby a stem 32 carried on a movable diaphragm wall 33 of the power element 16 will move to the left in FIG. 1 as the temperature in the oven 11 increases and, conversely, will move to the right in FIG. I as the temperature in the oven 11 decreases in a conventional manner.

The control device 14 includes another arm 34 having one end 35 fulcrumed to the housing 15 while the other end 36 thereof is interconnected to one end 37 of a tension spring 38. The other end '39 of the tension spring 38 is interconnected to the switch arm 24 between the contact-bridging end 23 and fulcrumed end 25 thereof as illustrated and as described in the US. patent to Wantz et al., No. 2,943,177.

The stem 32 of the temperature-responsive device 33 is adapted to engage against an intennediate part 40 of the arm 34 so as to cause clockwise movement of the end 36 of the arm 34 as the power element 16 is expanding upon an increase in temperature inthe oven 11. When the temperature of the oven 11 has reached or is slightly above the temperature selected by the manual manipulator means 20 in a manner hereinafter described, the movable wall 33 of the power element 16 has moved to the left in FIG. I a distance sufiicient to cause the clockwise movement of the end 36 of the am 34 to act through the tension spring 38 and snap the switch arm 24 in a counterclockwise direction so as to move the bridging end 23 thereof out of contact with the contacts 21 and 22 and, thereby, open the powerline L that leads to the sides 28 and 29 of the bake and broil heaters 12 and 13. Conversely, when the temperature of the oven 11 falls below the selected temperature, the power element 16 has collapsed to such a condition that the movement of the wall 33 to the right in FIG. I

causes sufficient counterclockwise movement of the end 36 of the arm 34 that the tension spring 38 causes clockwise movement of the switch arm 24 to close the switch 17 in the manner illustrated in FIG. 2 so as to interconnect the power source lead L to the sides 28 and 29 of the bake and broil heaters 12 and 13 for a purpose hereinafter described.

The amount of counterclockwise movement of the end 36 of the arm 34 is controlled by a movable plunger 41 of the housing 15 that has its axial position controlled by suitable cam means (not shown) of the manual manipulator means of the control device 14 in substantially the same manner as set forth in the aforementioned U.S. patent to Wantz et al.

In particular, the plunger 41 has a free end 42 that is adapted to be engaged by an intermediate part of the arm 34 to provide an adjustable stop against which further counterclockwise movement of the arm 34 will be prevented. Thus, when the manual manipulator means 20 of the control device 14 is set in its off position as illustrated in FIG. 1, the end 42 of the plunger 41 is so positioned in the control device 14 that the end 36 of the arm 34 completely prevents the switch arm 24 from closing the electrical switch 17 regardless of the temperature of the oven 11.

Accordingly, as the control knob or manual manipulator means 20 of the control device 14 is moved in either a clockwise or counterclockwise direction in the drawings from its off position illustrated in FIG. 1 through a bake range as illustrated in FIGS. 2 and 3 toward its high-temperature broil setting of FIG. 4, the end 42 of the plunger 41 is moved to the right in the drawings so that the switch 17 will be operated in response to the expansion and contraction of the temperature response device as set by the manual manipulator means 20 through a suitable interconnection therebetween, such as the interconnection fully described in the aforementioned US. patent to Wantz et al.

Accordingly, it can be seen that the electrical switch 17 of the control device 14 of this invention is thermostatically controlled and will open when the temperature of the oven 11 reaches the temperature that has been preselected by the manual manipulator means 20 and will again close when the temperature of the oven 11 falls below the preselected temperature.

The electrical switch 18 of the control device 14 includes a fixed contact 43 interconnected to the other side 44 of the bake heater 12 by a lead 45. Another fixed contract 46 of the switch 18 is interconnected to the other side 47 of the broil heater 13 by a lead 48, the lead 48 also interconnecting the side 47 of the broil heater 13 to a fixed contact 49 of the electrical switch 19. The electrical switch 18 includes a movable contact 50 carried on one end 51 of a switch arm 52 that has its other end 53 pivotally mounted and electrically interconnected to the power source lead L by a lead 54.

Similarly, the electrical switch 19 includes a movable contact 55 carried on one end 56 of a switch blade 57 pivotally mounted at its other end 58 as well as being interconnected to the neutral line N by a lead 59.

The position of the movable contacts 50 and 55 of the electrical switches 18 and 19 are controlled by the manual manipulator means 20 in a manner hereinafter described so as to place only the movable contact 50 against the fixed contact 43 when the manual manipulator means 20 is set in any bakeoperating position below a predetermined bake temperature, such as 300 F., as illustrated in FIG. 2.

When the manual manipulator means 20 is set for a higher bake temperature, such as between the predetermined tem' perature of 300 F as illustrated in FIG. 2 and the broil setting thereof as illustrated in FIG. 4, both movable contacts 50 and 55 are respectively placed against the fixed contacts 43 and 49 of the electrical switches 18 and 19 as illustrated in FIGS. 3 and 3A.

When the manual manipulator means 20 is set in its broil position, only the movable contact 50 of the switch 18 is placed against the fixed contact 46 as illustrated in FIG. 4.

While various means can be utilized to so interconnect the manual manipulator means 20 to the switch blades 52 and 57 to provide the above operation of the movable contacts 50 and 55, one such arrangement is illustrated in the drawings and comprises a rod or plunger 60 having four fixed and spaced retainers 61, 62, 63 and 64 thereon while the lower end 65 of the rod 60 engages against suitable cam means (not shown) on the manual manipulator means 20 which will position the rod means 60 in the various operating positions illustrated in the drawings relative to the housing means 15 in a manner similar to the cam-operated rod means disclosed in the aforementioned U.S. patent to Wantz et al.

The push rod 60 has its end 65 maintained against the cam means of the manual manipulator means 20 by a compression spring 66 acting against the upper retainer 61 thereof.

The switch blade 52 is disposed between the retainers 62 and 63 of the rod 60 and is nonnally urged to follow the movement of the retainer 62 by a compression spring 67 disposed between the retainer 63 and the switch blade 52 as illustrated in FIG. 1.

The switch blade 57 has a natural resiliency to remain the the position illustrated in FIG. 1 whereby such natural resilieney of the switch blade 57 holds the movable contact 55 of the switch 19 out of contact with the fixed contact 49 thereof. However, the retainer 64 of the push rod 60 is adapted to overcome the natural resiliency of the switch blade 57 to move the same upwardly in the manner illustrated in FIG. 3 for a purpose hereinafter described.

The operation of the control system 10 of this invention will now be described.

When the manual manipulator means 20 of the control device 14 of this invention is set in the off position, as illustrated in FIG. 1, the cam means of the manipulator means 20 is so constructed and arranged that the same causes the rod 60 to be disposed in the position illustrated in FIG. 1 so that the movable contact 50 of the electrical switch 18 is out of contact with both fixed contacts 43 and 46 thereof while the movable contact 55 of the electrical switch 19 is out of contact with its fixed contact 49. Also, the off position of the manual manipulator means 20 so positions the rod 41 to hold the arm 34 of the control device 14 in a manner to prevent the switch arm 24 of the switch 17 from closing against the contacts 21 and 22 regardless of the temperature of the oven 11.

Thus, it can be seen that in the off position of the control system 10 of this invention, both sides of the bake and broil heaters 12 and 13 are completely disconnected from the power source.

When the housewife of the like desires to utilize the oven 11 for a baking operation that is to be below the predetermined temperature of 300 F., the housewife or the like turns the manual manipulator means 20 to such selected temperature below the predetermined temperature of 300 F. as illustrated in FIG. 2 wherein not only is the axial position of the push rod 41 and temperaturesensing device 16 adjusted to the right for such a temperature setting, but also the plunger 60 is moved vertically upwardly in the drawings whereby the spring means 67 carries the switch blade 52 therewith to place the movable contact 50 of the switch 18 against the fixed contact 43 as illustrated in FIG. 2. However, such upward movement of the rod 60 is not sufficient to cause the retainer 64 to move the movable contact 55 of the switch 19 against the fixed contact 49 until the manipulator means 20 is moved into a temperature position above the predetermined temperature of 300 F. as illustrated in FIG. 3.

Thus, at a setting of the manipulator means 20 below the predetermined temperature of 300 F., the bake heater 12 is placed across the power source lines L and L whenever the switch 17 is closed as illustrated in FIG. 2 to provide substantially full rated power of the bake heater 12. When the temperature in the oven 11 reaches the selected temperature as set by the control device in FIG. 2, the switch 17 is opened by the expanding power element 16 to disconnect the bake heater 12 from the power source lead 1. whereby no heat Thus, during a baking operation wherein the manual manipulator means is set at a baking temperature belowv the predetermined te perature of 300 F only the bakeheater 12 is cycled on and off to tend to maintain the oven at the selected temperature.

However, should the housewife or the like desire to utilize the oven 11 at a baking temperature above the 300 F. and

below the broil setting of the oven 11, the housewife or the like moves the manual manipulator means 20 to such a selected temperature in the manner illustrated in FIG. 3 wherein not only is the power element 16 further moved to the right in the drawings to adjust the temperature setting in the thermostatic switch 17 to the higher temperature setting thereof, but also to further move the rod 60 upwardly so as to cause the same to place both movable contacts50 and 55 of the switches 18 and l9against their respective fixed contacts 43 and 49 as illustrated.

With this setting of the control system l0, it can be seen that when the thermostatic switch 17' is closed because the temperature of the oven 11 is below the selected high baking temperature, the bake heater 12 is placed across the power source leads L and L for substantially full rated power thereof while the broil heater 13 is placed across the powerline L and the neutral line N to produce approximately one-quarter of the rated power thereof.

In particular, it is well known that the wattage input varies directly as the voltage squared and inversely with the resistance (power equals E divided by R) whereby the thermal input for a high-temperature bake setting above the 300 F. for the disclosed arrangement will be substantially full-rated power for the bake heater 12 and one-fourth rated power for the broil element 13 each time the thermostatic switch 17 is closed.

Thus, should the bake and broil heaters 12 and 13 each be a '3,000-watt element and the power source be a 220-volt system, the bake and broil heaters 12 and 13 will provide a thermal input to the oven 11 of approximately 3,750 watts each time the thermostatic switch 17 is closed.

However, when the temperature in the oven 11 reaches the selected high baking temperature, the electrical switch 17 opens in the manner illustrated in FIG. 3A whereby the closed condition of electrical switches 18 and 19 causes the bake heater l2 and broil heater 13 to be placed in series across the powerline L and neutral line N so that both heaters and 13 will only be operating at part-rated power.

For example, when the bake and broilsheaters 12 and 13 are of the previously described type, the opening of the thermostatic switch 17 as illustrated in FIG. 3A causes the thermal input of the heaters 12 and 13 to be approximately one-sixteenth of the full-rated wattage thereof, since only one-fourth of the rated voltage appears across. eachheaterl2 and 13 so that only a 37 5-watt input is supplied by the'heaters l2 and l3 when the thermostatic switch 17 is in its opened position.

It has been found that the 375 watts being supplied by the heaters 12 and 13 in the manner illustrated in FIG. 3A is a heat input into the oven 11 less than the normal heat loss for the oven 11 when the oven 11 is set for a baking range above the 300 F. predetermined temperature.

Therefore, it can be seen that the total heat input for the oven 11 is not completely terminated when the temperature in v the oven 11 reaches the selected high baking temperature and is only reduced whereby the overall overshoot and undershoot range of the temperature of the oven 11 for any set high bak1- ing temperature thereof is held to a minimum which would not be the case should the heat input to the oven be completely terminated each time the thermostatic switch 17 is opened.

. When the housewife or the like desires to utilize the oven 11 for a broiling operation, the manual manipulator means 20 is moved to the broil position as illustrated in FIG. 4 wherein the temperature-responsive device 16 is further moved to the right to set the temperature setting for the thermostatic switch 17. However, in the broil position of the manipulator means 20, the cam means of the manipulator means 20 causes the rod 60 to move downwardly to carry the switch blade 52 therewith and place the movable contact 50 of the switch 18 against the fixed contact 46 so that only the broil heater 13 will be operatively interconnected to the power source across the power source lines L and L for substantially full rated power of the broil element 13 as long as the thermostaticswitch 17 is closed.

Therefore, it can be seen that this invention not only provides an improved control system and method for operating an electrical oven of a cooking apparatus or the like, but also this invention provides an improved control device for such a system or the like.

While the form of the invention now preferred has been disclosed as required by the statutes, other forms may be used, all coming within the scope of the claims which follow.

What is claimed is:

1. An electrical oven control system comprising a bake heater, a broil heater, an electrical power source, a control means having a thermostatically operated electrical switching arrangement having contact means in a line that is common to both said bake and broil heaters, and means operatively interconnecting said control means to said power source'and said control means to said heaters, said switching arrangement of said control means having a first temperature-sensing condition thereof for operating said bake heater at substantially full rated'power with said source and said broil heater at part rated power with said source when said control means is set in a position thereof for maintaining a selected bake temperature below a broil temperature and above a predetermined bake temperature when the temperature of said oven is belowsaid selected bake temperature and as long as said switching arrangement is in said first condition thereof, said switching arrangement operating both of said bake and broil heaters at part-rated power thereof with said source when the temperature of said oven is above said selected bake temperature and as long as said switching arrangement is in said first condition thereof, said control means setting said switching arrangement in another temperature-sensing condition thereof for only operating said bake heater at substantially full rated power with said source when said control means is set in a position thereof for maintaining another selected bake temperature below said predetermined temperature when the temperature of said oven is below said other selected bake temperature and as long as said control means is set at said other selected bake temperature, said switching arrangement terminating the operation of said bake heater when the temperature of said oven is above said; other selected bake-temperature and as long as said control means is set at said other selected bake temperature.

2. An electrical oven control system as set forth in claim 1, wherein said control means sets said switching arrangement in a third temperature-sensing condition thereof for only operating said broil heater at substantially full rated power when said control means is set in a position thereof for maintaining a broil temperature when the temperature of said oven is below said set broil temperature and as long as said switching arrangement is in said third condition thereof.

3. An electrical oven control system comprising a bake heater, a broil heater, a three-wire power source comprising a neutral line and two powerlines, a control means having a thermostatically operated electrical switching arrangement having contact means in one of said powerlines that is common to both said bake and broil heaters, and means operatively interconnecting said control means to said power source and said control means to said heaters, said switching arrangement of said control'means having a first temperature-sensing condition thereof for interconnecting said bake heater across said powerlines for substantially full rated power of said bake heater when said control means is set in a position thereof for maintaining a selected bake temperature in said oven below a broil temperature and above a predetermined bake temperature while interconnecting said broil heater across said neutral line and one of said powerlines for approximately one-quarter rated power of said broil heater when the temperature in said oven is below said selected bake temperature and as long as said switching arrangement is in said first condition thereof, said switching arrangement interconnecting said bake and broil heaters in series across said neutral line and one of said powerlines when the temperature in said oven is above said selected bake temperature and as long as said switching arrangement is in said first condition thereof to provide approximately one-sixteenth of the rated power of said heaters, said control means setting said switching arrangement in another temperature-sensing condition thereof for only interconnecting said bake heater across said powerlines for substantially full rated power of said bake heater when said control means is set in a position thereof for maintaining another selected bake temperature below said predetermined temperature when the temperature of said oven is below said other selected bake temperature and as long as said control means is set at said other selected bake temperature, said switching arrangement disconnecting said bake heater from said power source when the temperature of said oven is above said other selected bake temperature and as long as said control means is set at said other selected bake temperature.

4. An electrical oven control system as set forth in claim 3 wherein said control means sets said switching arrangement in a third temperature-sensing condition thereof for only interconnecting said broil heater across said power lines for substantially full rated power of said broil burner when said control means is set in a position thereof for maintaining a broil temperature when the temperature of said oven is below said set broil temperature and as long as said switching arrangement is in said third condition thereof.

5. An electrical oven control system as set forth in claim 3 wherein said switching arrangement has a first electrical switch in one of said powerlines and has a temperatureresponsive device for opening and closing said first electrical switching in response to oven temperature.

6. An electrical oven control system as set forth in claim 5 wherein said control means has manual manipulator means for adjusting said temperature-responsive device to select the oven temperature that will effect opening of said first electrical switch.

7. An electrical oven control system as set forth in claim 6 wherein said switching arrangement has a second electrical switch to interconnect the other of said powerlines to one side of said bake heater when said second switch is closed, said bake heater having the other side thereof interconnected to said one powerline downstream of said first switch.

8. An electrical oven control system as set forth in claim 7 wherein said switching arrangement has a third electrical switch to interconnect said neutral line to one side of said broil heater when said third switch is closed, said broil heater having the other side thereof interconnected to said one powerline downstream of said first switch.

9. An electrical oven control system as set forth in claim 8 wherein said manual manipulator means of said control means is operatively interconnected to said second switch to only close said second switch when setting said control means in a bake temperature setting below said predetermined temperature so that only said bake heater will be operated by said power source when said first switch is closed by said temperature-responsive means.

10. An electrical oven control system as set forth in claim 9 wherein said manual manipulator means of said control means is operatively interconnected to said third switch to close said second and third switches when setting said control means in a bake temperature setting between said predetermined ternperature and said broil temperature so that said bake heater lS interconnected across said powerlines and said broil heater is interconnected across said neutral line and said one powerline when said first switch is closed by said temperature-responsive device and so that said bake heater and broil heater are placed in series across said other powerline and said neutral line when said first switch is opened by said temperature-responsive device.

11. An electrical control system as set forth in claim 9 wherein said second switch of said control means has another closed position thereof different than said first-named closed position thereof, said second switch interconnecting said other powerline to said one side of said broil heater when said second switch is in said other closed position thereof.

12. An electrical control system as set forth in claim 11 wherein said manual manipulator means only closes said second switch in said other closed position thereof when said manual manipulator means is set in a broil setting whereby only said broil heater will be interconnected to said power source across said powerlines thereof when said first switch is closed by said temperature-responsive means. 

1. An electrical oven control system comprising a bake heater, a broil heater, an electrical power source, a control means having a thermostatically operated electrical switching arrangement having contact means in a line that is common to both said bake and broil heaters, and means operatively interconnecting said control means to said power source and said control means to said heaters, said switching arrangement of said control means having a first temperature-sensing condition thereof for operating said bakE heater at substantially full rated power with said source and said broil heater at part rated power with said source when said control means is set in a position thereof for maintaining a selected bake temperature below a broil temperature and above a predetermined bake temperature when the temperature of said oven is below said selected bake temperature and as long as said switching arrangement is in said first condition thereof, said switching arrangement operating both of said bake and broil heaters at part-rated power thereof with said source when the temperature of said oven is above said selected bake temperature and as long as said switching arrangement is in said first condition thereof, said control means setting said switching arrangement in another temperature-sensing condition thereof for only operating said bake heater at substantially full rated power with said source when said control means is set in a position thereof for maintaining another selected bake temperature below said predetermined temperature when the temperature of said oven is below said other selected bake temperature and as long as said control means is set at said other selected bake temperature, said switching arrangement terminating the operation of said bake heater when the temperature of said oven is above said other selected bake temperature and as long as said control means is set at said other selected bake temperature.
 2. An electrical oven control system as set forth in claim 1, wherein said control means sets said switching arrangement in a third temperature-sensing condition thereof for only operating said broil heater at substantially full rated power when said control means is set in a position thereof for maintaining a broil temperature when the temperature of said oven is below said set broil temperature and as long as said switching arrangement is in said third condition thereof.
 3. An electrical oven control system comprising a bake heater, a broil heater, a three-wire power source comprising a neutral line and two powerlines, a control means having a thermostatically operated electrical switching arrangement having contact means in one of said powerlines that is common to both said bake and broil heaters, and means operatively interconnecting said control means to said power source and said control means to said heaters, said switching arrangement of said control means having a first temperature-sensing condition thereof for interconnecting said bake heater across said powerlines for substantially full rated power of said bake heater when said control means is set in a position thereof for maintaining a selected bake temperature in said oven below a broil temperature and above a predetermined bake temperature while interconnecting said broil heater across said neutral line and one of said powerlines for approximately one-quarter rated power of said broil heater when the temperature in said oven is below said selected bake temperature and as long as said switching arrangement is in said first condition thereof, said switching arrangement interconnecting said bake and broil heaters in series across said neutral line and one of said powerlines when the temperature in said oven is above said selected bake temperature and as long as said switching arrangement is in said first condition thereof to provide approximately one-sixteenth of the rated power of said heaters, said control means setting said switching arrangement in another temperature-sensing condition thereof for only interconnecting said bake heater across said powerlines for substantially full rated power of said bake heater when said control means is set in a position thereof for maintaining another selected bake temperature below said predetermined temperature when the temperature of said oven is below said other selected bake temperature and as long as said control means is set at said other selected bake temperature, said switching arrangement disconnecting said bake heater from said power source when the teMperature of said oven is above said other selected bake temperature and as long as said control means is set at said other selected bake temperature.
 4. An electrical oven control system as set forth in claim 3 wherein said control means sets said switching arrangement in a third temperature-sensing condition thereof for only interconnecting said broil heater across said power lines for substantially full rated power of said broil burner when said control means is set in a position thereof for maintaining a broil temperature when the temperature of said oven is below said set broil temperature and as long as said switching arrangement is in said third condition thereof.
 5. An electrical oven control system as set forth in claim 3 wherein said switching arrangement has a first electrical switch in one of said powerlines and has a temperature-responsive device for opening and closing said first electrical switching in response to oven temperature.
 6. An electrical oven control system as set forth in claim 5 wherein said control means has manual manipulator means for adjusting said temperature-responsive device to select the oven temperature that will effect opening of said first electrical switch.
 7. An electrical oven control system as set forth in claim 6 wherein said switching arrangement has a second electrical switch to interconnect the other of said powerlines to one side of said bake heater when said second switch is closed, said bake heater having the other side thereof interconnected to said one powerline downstream of said first switch.
 8. An electrical oven control system as set forth in claim 7 wherein said switching arrangement has a third electrical switch to interconnect said neutral line to one side of said broil heater when said third switch is closed, said broil heater having the other side thereof interconnected to said one powerline downstream of said first switch.
 9. An electrical oven control system as set forth in claim 8 wherein said manual manipulator means of said control means is operatively interconnected to said second switch to only close said second switch when setting said control means in a bake temperature setting below said predetermined temperature so that only said bake heater will be operated by said power source when said first switch is closed by said temperature-responsive means.
 10. An electrical oven control system as set forth in claim 9 wherein said manual manipulator means of said control means is operatively interconnected to said third switch to close said second and third switches when setting said control means in a bake temperature setting between said predetermined temperature and said broil temperature so that said bake heater is interconnected across said powerlines and said broil heater is interconnected across said neutral line and said one powerline when said first switch is closed by said temperature-responsive device and so that said bake heater and broil heater are placed in series across said other powerline and said neutral line when said first switch is opened by said temperature-responsive device.
 11. An electrical control system as set forth in claim 9 wherein said second switch of said control means has another closed position thereof different than said first-named closed position thereof, said second switch interconnecting said other powerline to said one side of said broil heater when said second switch is in said other closed position thereof.
 12. An electrical control system as set forth in claim 11 wherein said manual manipulator means only closes said second switch in said other closed position thereof when said manual manipulator means is set in a broil setting whereby only said broil heater will be interconnected to said power source across said powerlines thereof when said first switch is closed by said temperature-responsive means. 